Greenhouse gas concentrations

Carbon dioxide concentrations in the atmosphere

Carbon dioxide (CO₂) is the most important greenhouse gas. It is responsible for approximately 66% of the radiative forcing that is currently observed.^{Footnote 1}

Key results

• Globally, annual average carbon dioxide (CO₂) concentration increased by 25%, from 338.9 parts per million (ppm) to 422.8 ppm between 1980 to 2024
• In Canada, annual average concentration of CO₂ increased by 25%, from 339.6 ppm to 426.0 ppm over the period spanning 1980 to 2024
• In 2024, the average concentration of CO₂ in Canada was 426.0 ppm, up from 422.4 ppm in 2023, the largest anual increase since 1980

Carbon dioxide concentrations, Canada and global, 1980 to 2024

How this indicator was calculated

Note: From 1980 to 1999, averages were calculated based on data from 2 to 3 sampling stations. Since 1999, data from 5 sampling stations are used to represent CO₂ concentrations. Due to some site closures during the COVID-19 pandemic, data from Canada between 2020 and 2022 were interpolated based on data from the Alert station, which remained active throughout that period. Additionally, due to access issues, data for the Estevan Point (ESP) site were synthesized between 2023 and 2024. Global annual averages are based on measurements from sampling stations that are part of the Global Greenhouse Gas Reference Network.
Source: Environment and Climate Change Canada (2025) Climate Research Division, Canadian Greenhouse Gas Measurement Program and National Oceanic and Atmospheric Administration (2025) Global Monitoring Laboratory - Trends in Atmospheric Carbon Dioxide.

In 2024, the global average concentration of CO₂ reached a new high of 422.8 ppm, up from 419.4 in 2023. In the pre-industrial era (prior to 1750), global CO₂ concentration was about 278 ppm.^{Footnote 2}

In Canada, the rate at which CO₂ concentrations are changing has also increased. In the 1990s, the annual increase in CO₂ was around 1.5 ppm. In the last decade, concentrations have increased by about 2.6 ppm per year. Seasonal cycles can also be observed with lower concentrations in summer due to photosynthetic uptake (plants remove CO₂ from the atmosphere) and higher concentrations in winter due to the decay of plant material (breakdown of organic material releases CO₂).

The COVID-19 pandemic created an economic slowdown in 2020 and 2021 and important reductions in travel by air and land. This resulted in a reduction in anthropogenic CO₂ emissions, in Canada and worldwide. However, there was no recognizable impact on CO₂ concentrations between 2020 and 2022.

Methane concentrations in the atmosphere

Methane is the second most important greenhouse gas generated by human activity. It is currently responsible for approximately 16% of the radiative forcing.^{Footnote 1}

Key results

• Globally, annual average methane concentration increased by 16%, from 1 670 parts per billion (ppb) to 1 930 ppb between 1986 to 2024
• In Canada, the annual average concentration of methane also increased by 14%, from 1 764 ppb to 2 016 ppb between 1986 to 2024
• In 2024, the average concentration of methane in Canada was 2 016 ppb, up from 2 009 ppb in 2023

Methane concentrations, Canada and global, 1986 to 2024

How this indicator was calculated

Note: From 1986 to 1999, averages in Canada were calculated based on data from 1 to 2 sampling stations. Since 1999, data from 5 sampling stations are used to represent CH₄ concentrations. Due to some site closures during the COVID-19 pandemic, data from Canada between 2020 and 2022 were interpolated based on data from the Alert station, which remained active throughout that period. Additionally, due to access issues, data for the Estevan Point (ESP) site was synthesized between 2023 and 2024. Global annual averages are based on measurements from sampling stations that are part of the Global Greenhouse Gas Reference Network.
Source: Environment and Climate Change Canada (2025) Climate Research Division, Canadian Greenhouse Gas Measurement Program and National Oceanic and Atmospheric Administration (2025) Global Monitoring Laboratory - Trends in Atmospheric Methane.

In 2024, the global average concentration of methane reached a new high of 1 930 ppb, an increase of 8 ppb from 2023. This increase is slightly lower than that observed in 2022 to 2023 and is close to the average annual increase over the past decade. Pre-industrial global methane concentrations were just under 730 ppb.^{Footnote 2}

Since 2010, average methane concentrations in Canada and globally have been increasing at a faster rate. In the 2000s, an increase of about 3 ppb/year was observed. In the 2010s, the increasing rate reached 8.5 ppb/year and the increase has reached 12 ppb/year since 2021. Although no definitive cause has been identified to explain this increase, stable isotope^{Footnote 3} measurements of atmospheric methane strongly suggest that increases in wetland emissions in the tropics may be responsible.^{Footnote 2}

Methane concentrations are higher in the northern hemisphere because both natural and human caused sources of methane are more abundant there.^{Footnote 4}  As a result, annual changes in observed methane concentrations in Canada are similar to annual changes observed across the globe, but the magnitude is typically around 85 ppb higher.  Globally, approximately 40% of the methane emitted to the atmosphere is from natural sources such as wetlands. The remaining 60% of emissions are due to anthropogenic (human caused) sources such as cattle ranching, agriculture, burning of fossil fuels and landfills.

About the indicator

What the indicator measures

The indicator shows the trends in concentrations for 2 greenhouse gases: carbon dioxide (CO₂) and methane (CH₄). Concentrations are presented on monthly and annual bases for Canada. The indicator also includes the global annual average concentrations.

Why this indicator is important

Greenhouse gases (GHGs) trap heat in the Earth's atmosphere, just as the glass of a greenhouse keeps warm air inside. Human activity increases the amount of GHGs in the atmosphere, contributing to a warming of the Earth's surface. This is called the enhanced greenhouse effect. The release of GHGs and their increasing concentrations in the atmosphere are having significant impacts on the environment, human health and the economy. 

This indicator serves to identify trends and seasonal variability of carbon dioxide and methane concentrations in Canada. It provides a coherent and consistent picture of the current and past states of these 2 greenhouse gases in the atmosphere, as a result of changing atmospheric transport patterns, emissions from natural sources and emissions to the atmosphere due to human activities.

GHG measurements improve our understanding of natural and anthropogenic sources of GHGs, the role of GHGs in warming the atmosphere, as well as the processes that govern the transport and fate of GHGs in the biosphere. GHG measurements in the atmosphere complement other key indicators used to assess progress in mitigating climate change by reducing GHG emissions. Since GHGs are long-lived in the atmosphere, atmospheric measurements are an indicator of the global and domestic efforts to date to address GHG emissions.

Related indicators

The Greenhouse gas emissions indictor reports trends in total anthropogenic (human-made) GHG emissions at the national level, per person and per unit gross domestic product, by province and territory and by economic sector.

The Global greenhouse gas emissions indicator provides a global perspective on Canada's share of global GHG emissions.

The Greenhouse gas emissions from a consumption perspective indicator shows the impact of Canada's consumption of goods and services, regardless of where they are produced, on the levels of greenhouse gas released into the atmosphere.

The Greenhouse gas emissions projections indicator provides an overview of Canada's projected GHG emissions for the next several years.

The Greenhouse gas emissions from large facilities indicator reports GHG emissions from the largest GHG emitters in Canada (industrial and other types of facilities).

The Land-based greenhouse gas emissions and removal indicator provides annual estimates of Canada's GHG emissions and removals from managed lands.

Data sources and methods

Data sources

Concentration data used for these indicators were retrieved from the Canadian Greenhouse Gas Measurement Program of the Climate Research Division of Environment and Climate Change Canada. The indicators are calculated using the greenhouse gas concentrations measured at the Alert (NU), Sable Island (NS), Estevan Point (BC), Fraserdale (ON) and East Trout Lake (SK) monitoring stations. The final ambient concentrations of carbon dioxide (CO₂) and methane (CH₄) are averaged to estimate the annual and monthly indicators values.

Global average annual concentrations were obtained from the National Oceanic and Atmospheric Administration's Global Monitoring Laboratory (NOAA), which developed the Carbon Cycle Greenhouse Gases research program. 

More information

Canadian Greenhouse Gas Monitoring Network

Environment and Climate Change Canada has been continually building a long-term observation network for atmospheric measurements of CO₂, CH₄ and carbon monoxide (CO), which currently stands at 16 core continuous observational ground-based sites. These sites are spread across the country in coastal, interior and arctic regions, with the aim of providing high quality data to observe and monitor natural sources and sinks, and anthropogenic (human-caused) sources of greenhouse gases in Canada.

The data used for the indicators were measured at 3 coastal sites and 2 mid-continental forest sites that are part of the Canadian Greenhouse Gas Monitoring Network. These 5 stations were selected for the representativeness of their spatial and temporal coverage. Table 1 below provides more specific information on each of the stations.

The coastal sites are located at:

• Alert (NU), on Ellesmere Island in the Canadian high Arctic
• Sable Island (NS), located in the Atlantic Ocean
• Estevan Point (BC), a lighthouse station located on the coastline of Vancouver Island. Estevan Point became the replacement station for Cape St. James in 1992, when the weather station at Cape St. James was automated and no longer required a manned presence on site.

The mid-continental forest monitoring stations are situated in:

• Fraserdale (ON), located 150 km north of Timmins (ON)
• East Trout Lake (SK), located 150 km north-east of Prince Albert (SK). It became the replacement station for Candle Lake in 2005.

The Alert Station is also an official World Meteorological Organization Global Atmosphere Watch Program (WMO-GAW) station, one of 26 global stations around the world. Alert is the most northerly site in the WMO-GAW Network. The Alert site is also one of 3 sites, along with Mauna Loa and Cape Grim, which have been identified by the WMO-GAW as official greenhouse gas intercomparison sites.

Greenhouse gas concentration monitoring stations in Canada, 2025

Data table for the long description

Table 1. Greenhouse gas concentration monitoring stations in Canada

Start date	Site name (3 letter station code)	Coordinates	Elevation (Above Sea Level)	Intake height	Insitu parameters	Insitu instrumentation	Flask sampling frequency (for CO2, CH4, CO, N2O, SF6)
March, 1975	Sable Island, Nova Scotia (WSA)	43.932237N, 60.009275W	5m	25m	CO2, CH4, CO	NDIR[A], GC[B], CRDS[C]	Single flask every 3 days
July, 1975	Alert, Nunavut (ALT)	82.450833N, 62.507222W	200m	10m	CO2, CH4, CO, N2O	NDIR[A], GC[B], CRDS[C],OA-ICOS[D]	One pair of flask each week
January, 1990	Fraserdale, Ontario (FRD)	49.875222N, 81.570083W	210m	40m	CO2,CH4, CO, N2O, SF6	NDIR[A], GC[B], CRDS[C]	Single flask once per week (in the afternoon)
June, 1992	Estevan Point, British Columbia (ESP)	49.382954N, 126.544101W	7m	40m	CO2, CH4, CO	NDIR[A], GC[B], CRDS[C]	One pair of flask once per week
August, 2005	East Trout Lake, Saskatchewan(ETL)	54.354130N, 104.986835W	493m	105m	CO2,CH4, CO, N2O, SF6	NDIR[A], GC[B], CRDS[C]	Single flask once per week (in the afternoon

Note: ^[A] Non-Dispersive Infrared, ^[B] Gas Chromatography, ^[C]Cavity Ring-Down Spectroscopy, ^[D]Off-Axis Integrated Cavity Output Spectroscopy.

Note: The map displays the location of the 5 long-term greenhouse gas concentration monitoring stations of used in the indicator: Alert (NU), Sable Island (NS), Fraserdale (ON) East Trout Lake (SK) and Estevan Point (BC). Only Alert remained continuously active from 2020 to 2022. For more information on the core monitoring stations, please refer to Table 1 above.
Source: Environment and Climate Change Canada (2025) Climate Research Division, Canadian Greenhouse Gas Measurement Program.

Temporal coverage

The indicator presenting the carbon dioxide (CO₂) concentrations covers the period from 1980 to 2024.

The methane (CH₄) concentrations at the national and global levels were calculated using data for the years 1986 to 2024.

Data availability

Greenhouse gas observations at the 5 monitoring stations are all currently operated continuously and provide hourly, daily and monthly data. Prior to 1988, carbon dioxide (CO₂) observations were monitored using weekly grab (flask) sampling procedures.

Data availability varies by station and by greenhouse gas over time. The following table shows the time periods for which data are available for each greenhouse gas at the 5 monitoring stations.

Table 2. Data availability by greenhouse gas and monitoring station

Greenhouse gas	Time period	Monitoring stations
Carbon dioxide	1980 to 2024	Alert
Carbon dioxide	1980 to 2024	Sable Island[A]
Carbon dioxide	1980 to 2024	Estevan Point/Cape St. James[A][B]
Carbon dioxide	1999 to 2024	Fraserdale[A]
Carbon dioxide	2002 to 2024	East Trout Lake/Candle Lake[A]
Methane	1985 to 2024	Alert
Methane	1999 to 2024	Sable Island[A]
Methane	1999 to 2024	Estevan Point/Cape St. James[A][B]
Methane	1990 to 2024	Fraserdale[A]
Methane	2002 to 2024	East Trout Lake/Candle Lake[A]

Note: ^[A] For the years 2020 to 2022, data is incomplete due to site closures as a result of the COVID-19 pandemic.^[B] For the years 2023 to 2024, data is incomplete for the Estevan Point (ESP) due to access issues.

Global concentrations from the Carbon Cycle Greenhouse Gases research program

The Carbon Cycle Greenhouse Gases research program from the National Oceanic and Atmospheric Administration's Global Monitoring Laboratory operates the Global Greenhouse Gas Reference Network, measuring the atmospheric distribution and trends of the 3 main long-term drivers of climate change [carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O)] as well as carbon monoxide (CO). 

Methods

The monthly and annual concentrations are an average of the daily values over the corresponding period of time.

For the years 2020 to 2022, a large amount of data at the national level are missing as a result of site closures during the COVID-19 pandemic. To calculate the monthly and annual concentrations over Canada for these years, concentrations were interpolated based on long-term trends observed at the Alert site and the average of the mean seasonal cycles observed at all 5 sites.

Caveats and limitations

Since greenhouse gases (GHG) are long-lived in the atmosphere and are transported globally from the site of emission, these indicators are an integrated measure of global and domestic GHG emissions to the atmosphere. For more information on Canada's emissions, and to assess Canada's progress in reducing its emissions, please refer to the related indicators which present information on greenhouse gas emissions in Canada.

For both carbon dioxide and methane concentrations, the number of monitoring stations used in the analyses increased in 1999. The change in the number of monitoring sites may have influenced calculations of the average values and make it difficult to compare trends prior and post 1999. In the particular case of methane concentrations, values prior to 1999 were based on data from a single station and may not be representative of the concentrations over Canada.

Due to the COVID-19 pandemic, many monitoring stations were out of operation for much of 2020 to 2022. As such, monthly and annual values were interpolated from the trends observed at Alert and the seasonal variations observed at the 5 monitoring stations. This method may miss inter-annual variations related to sub-regional scale emission changes in Canada.

Resources

References

Environment and Climate change Canada (2025) Canadian Greenhouse Gas Measurement Program. Retrieved on May 27, 2025.

Intergovernmental Panel on Climate Change (2022) Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Retrieved on Retrieved on May 27, 2025.

National Oceanic and Atmospheric Administration (2025) Carbon cycle greenhouse gases. Retrieved on Retrieved on May 27, 2025.

National Oceanic and Atmospheric Administration (2025) Global monitoring laboratory - Trends in atmospheric carbon dioxide. Retrieved on May 27, 2025.

World Data Centre for Greenhouse Gases (2018) Data archive. Retrieved on May 27, 2025.

World Meteorological Organization (2023) Global Atmosphere Watch. Retrieved on May 27, 2025.

World Meteorological Organization (2025) WMO Greenhouse Gases Bulletins. Retrieved on May 27, 2025.

Related information

Canada's action on climate change

Canada's changing climate report

Climate change

Greenhouse gas emissions indicator

WMO Greenhouse Gases Bulletin

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